In theory, the designated driver concept holds great promise for reducing drunk driving. It is simple, inexpensive, almost universally recognized, and generally positively regarded by the U.S. population as a means for avoiding drunk driving. In practice, research has shown that implementing the designated driver concept is often flawed. To function properly, groups of drinkers must commit to three stages: (1) the group must designate a driver before starting to drink, (2) the designee must abstain from drinking, and (3) the designee must fulfill his/her responsibility to be the driver. Failure at any of these three stages of implementation could result in potentially impaired drivers either claiming to be the designated driver or usurping the role of the designated driver. The research proposed is designed to address factors that may impede proper implementation of the designated driver concept. Six intervention trials are proposed. These are designed to (1) cue the use of designated drivers, (2) change the attitudes of the group, and (3) affect group norms to support the proper use of designated drivers. Each trial will use random assignment and will be conducted at the San Ysidro border crossing. There, on weekend and Wednesday nights, thousands of young San Diegans cross into Tijuana to patronize bars and clubs and to engage in binge drinking. Most park cars on the U.S. side and walk across the border. An existing NIAAA-funded longitudinal survey is underway, assessing blood alcohol concentration (BAC) and behavioral tendencies of crossers from U.S. to Tijuana (and back). Alcohol breath tests are administered to participants when arriving and departing. Though conducted on different nights than the existing longitudinal survey, the intervention trials proposed here will build upon our experience with the existing survey. Further, the methods used will recruit whole groups, so that these trials will offer an opportunity to study the effects of a designated driver on the results of passengers' BACs.